Website looking scrambled in Vivaldi

A website on our intranet is looking quite odd in Vivaldi, while it looks perfectly normal in Explorer/Firefox.
This is running on Windows 7. I do see the issue with being unable to link the actual site, but seeing it's on the company intranet, you'll have to forgive me.
Anyone got any ideas?
Explorer:

@gwen-dragon First of all, I really appreciate your assistance.
I tried spoofing to both IE10 and Firefox, no luck. I also installed Snapshot 1.12.
Unfortunately I'm very inexperienced dealing with these issues.